Effect of Mediterranean diet on liver enzymes: a systematic review and meta-analysis of randomised controlled trials

Elevated levels of liver enzymes are the main markers of liver dysfunction. Liver enzymes are the important indicators of non-alcoholic fatty liver disease (NAFLD) in the general population. Previous randomised clinical trials (RCT) investigated the effects of Mediterranean diet (MedDiet) as a plant-based diet on features of NAFLD like liver enzymes, but their results are contradictory. This study aimed to systematically review and meta-analyse RCT investigating the effect of MedDiet on liver enzymes. PubMed, Web of Science, Scopus and Google Scholar were searched until December 2020. A total of ten RCT (n 705 participants) evaluating the effect of MedDiet on liver enzymes including aspartate aminotransferase (AST), alanine transaminase (ALT) and gamma-glutamyltransferase (GGT) were included. A random effects model was used to estimate the pooled effect size. To evaluate the heterogeneity among the included studies, the Cochran's Q-test and I-squared test were used. The MedDiet significantly reduced AST (weighted mean difference (WMD) = -0 center dot 38 IU/l; 95 % CI - 0 center dot 73, -0 center dot 03 IU/l; P = 0 center dot 03) and GGT (WMD = -0 center dot 16 IU/l; 95 % CI - 0 center dot 32, -0 center dot 006 IU/l; P = 0 center dot 04) but had no significant effect on ALT (WMD = -0 center dot 55 IU/l; 95 % CI - 1 center dot 25, 0 center dot 13 IU/l; P = 0 center dot 11). However, sensitivity analysis revealed that the overall effects of MedDiet on AST, GGT and ALT were significantly influenced by removing some studies. There was no publication bias based on Begg's and Egger's tests. Generally, MedDiet can improve liver enzymes. To better conclusion, further RCT investigating the effect of MedDiet on liver enzymes, especially in patients with NAFLD, are still required.

Automated summary

This study reviewed RCT on the effect of Mediterranean diet on liver enzymes and found that it significantly reduced AST and GGT, but had no significant effect on ALT. Sensitivity analysis revealed that the overall effects were significantly influenced by some studies, suggesting a need for further research.